David Koschman died in 2004 after a confrontation with a group that included one of then-Mayor Richard Daley's nephews. Koschman's mom has a court fight to get a special prosecutor in the case. (Chicago Tribune)

Sworn witness interviews show Chicago police "deliberately falsified" reports during the investigation into the death of a young man during a drunken confrontation with a nephew of former Mayor Richard Daley's nearly eight years ago, attorneys asking for a special prosecutor argued Wednesday.

The 40-page court filing on behalf of the mother of David Koschman also alleged Cook County State's Attorney Anita Alvarez has opted to "circle the wagons" to block their bid for an independent investigation because of her political ties to Daley.

Attached to the filing in Cook County Circuit Court was a photo the lawyers said was taken from Alvarez's Facebook page showing her posing with Daley at the 2010 Mexican Independence Day parade. Another image of a newspaper clipping showed a young Alvarez grinning and shaking hands with Daley — then the Cook County state's attorney — on the day she was sworn in as a prosecutor in 1986.

Alvarez's decision to fight the appointment of a special prosecutor shows her "close ties to Richard Daley, who has a personal interest in the fate of his nephew, have compromised her ability to view the evidence with an open mind," according to the filing.

Koschman, 21, had been drinking in the Rush Street nightlife district early on April 25, 2004, when he argued with a group that included Daley's nephew, Richard "R.J." Vanecko. During the altercation, Koschman was punched or shoved, causing him to fall back and to hit his head on the street. He died 12 days later.

Four of Koschman's friends and two bystanders there that night were recently interviewed under oath in an investigation being conducted by the city inspector general's office. Prosecutors used portions of those interviews to argue last month that the witnesses were unreliable and had made conflicting statements to reporters for theChicago Sun-Times, which has published an investigative series on Koschman's death.

But attorneys for Koschman's mother, Nanci, argued in Wednesday's filing the transcripts show police mischaracterized witnesses' statements to make it falsely appear that Koschman was the physical aggressor in the altercation and that Vanecko could not be positively identified as the person who struck him.

According to the quoted transcripts, Michael Connolly, a bystander not with either side, said statements by prosecutors that Koschman had initiated the physical confrontation were a "flat-out lie." He also said police reports from 2004 stating he had seen Koschman move physically toward Vanecko were incorrect.

"I never said that I saw David moving forward to strike anybody," Connolly was quoted in the transcript as saying under oath. "I never said that in any (police) statement."

One of Koschman's friends, Shaun Hageline, said he was clear in his statements to police that Vanecko and his group were the ones who were physically imposing and that Vanecko, who towered over Koschman, appeared drunk but that police omitted that information from their reports.

"The notion of Dave Koschman beating these guys up or punching them or winning any kind of fight was just preposterous," the filing quoted Hageline as saying.

Vanecko ran from the scene that night. It wasn't until nearly a month later that detectives had him come in to the station for a lineup, but none of the witnesses identified him as the assailant.

In their sworn statements, several of Koschman's friends recently revealed that detectives told them after the lineup that Vanecko had tearfully apologized for his actions and said he never meant for one punch to lead to someone's death.

Koschman friend James Copeland recalled a detective telling him Vanecko was "in the other room and he's bawling his eyes out, he's a big baby."

Attorneys for the Koschman family questioned why the revelation was never described in police reports or mentioned by Alvarez and went on to call it "disturbing" that the detail might have gone unknown if prosecutors hadn't been forced to turn over the transcripts.